Prepare the Filling. In a skillet, heat olive oil and sauté onion, garlic, and bell pepper until softened. Stir in black beans, corn, cumin, and chili powder. Mash slightly with the back of a spoon to create a creamy, chunky filling.
Assemble the Quesadillas. Lay a tortilla flat, sprinkle with cheese, add a layer of black bean mixture, and top with more cheese. Place another tortilla on top (or fold in half for single-layer quesadillas).
Cook to Crispy Perfection. Heat a skillet or griddle over medium heat. Cook the quesadilla for 2–3 minutes per side until golden brown and the cheese has melted.
Slice and Serve. Cut into wedges and serve hot with salsa, sour cream, guacamole, or hot sauce.